The Cubs released Rex Brothers on Thursday, helping Riefenhauser's long-shot chances of making the Cubs out of camp.
He's probably still behind Travis Wood and Clayton Richard on the depth chart, but Riefenhauser and Eric Jokisch are the only other lefty relievers on the 40-man roster. Still, given his lack of success in the majors and the strong Cubs bullpen, Riefenhauser is more likely to begin the year in the minors.